1. Field of the Invention
The invention relates to an apparatus for identifying a page of printing plate or printed product to find and correct an error in page.
2. Description of Related Art
Preparatory to the printing of a printed product such as a newspaper, magazine, catalogue and the like which has some or many pages, a printing plate is processed for printing by a plate making apparatus after compilation and proof reading. The printing plate is then set up on a plate cylinder in a printing press for printing a web or sheets from page to page of printed product. Recently, the CTP (Computer to Plate) system has been commercialized in which the preparatory steps are computerized to automatically hard-copy the block copies and make an engraving onto the printing plate. It appears that in the future the CTC (Computer to Cylinder) system will be actualized which makes the engraving onto the printing plate set up on the plate cylinder in accordance with data transmitted from a computer.
In the case, however, if an operator finds an error in page of printed product after printing, it is required to correct the error in page in the preparatory steps and then start all the steps over again, taking labours and times, resulting in losses in film, printing plate and web or sheet. If the operator can not find the error in page, the printed products may be put on sale and transported. It is therefore required to call back the printed products having the error in page and resend the printed products after correcting, resulting in losses more and more.
Under the circumstances, it is desired to identify a page of printed product at many steps, so as to find and correct an error in page without taking labours and times and without resulting in losses. In this connection, it is unacceptable to put a bar cord on each page of printed product. Accordingly, a bar cord reader is unavailable to identify the page of printed product.
It is therefore an object of the invention to provide a new and improved apparatus for identifying a page of printing plate or printed product to find and correct an error in page, to overcome the above problems.
Another object of the invention is to identify a page of printing plate or printed product without putting an additional mark such as a bar cord on the page of printed product.
3. Summary of the Invention
According to the invention, there is provided an apparatus for identifying a page of printing plate or printed product. The apparatus comprises reading head means for reading out at least one of items in a local descriptive portion of the page of printing plate or printed product. The apparatus further comprises identifying means for identifying the page of printing plate or printed product in accordance with the read out data transmitted from the reading head means.
The item may include a character, brief description, mark, pattern or figure indicating the page, edition, version, kind or the like of printing plate or printed product.
The reading head means may comprise a CCD linear sensor and a light source which comprises LEDs.
In a preferred embodiment, the apparatus further comprises a managing system by which the position and range of the local descriptive portion is preset, the item in the local descriptive portion being previously stored as reference data in the managing system. The identifying means comprises comparing means for comparing the read out data transmitted from the reading head means with the reference data transmitted from the managing system to identify the page of printing plate or printed product.
The apparatus further comprises moving means for moving the reading head means longitudinally of the CCD linear sensor into a reading position corresponding to the local descriptive portion. The reading position is preset by the managing system.
The printing plate or printed product may be set up on a rotor. The CCD linear sensor extends axially of the rotor, the moving means moving the reading head means axially of the rotor into the reading position which is an axial position of the rotor. The local descriptive portion is defined with orthogonal axes X and Y of coordinates, one of the axes X extending axially of the rotor, the other axis Y extending circumferentially of the rotor. The reading head means has a reading range in one of the axes X, the reading range in one of the axes X being preset by the number of used pixel and the resolution of the CCD linear sensor. The reading head means starts to read out at a starting position in the other axis Y, a rotary encoder being mounted on the shaft of the rotor, the starting position in the other axis Y being preset by a counted value at a clock frequency synchronized with a signal output from the rotary encoder. The reading head means continues to read out within a reading range in the other axis Y, the reading range in the other axis Y being preset by a counted value in a preset dividing ratio of a frequency of the signal output from the rotary encoder.
The rotor may comprise a plate cylinder in a printing press, the printing plate being set up on the plate cylinder. The reading head means is located adjacent to the plate cylinder.
In another embodiment, the printing plate or printed product is fed in a feeding direction, the CCD linear sensor extending perpendicular to the feeding direction. The local descriptive portion is defined with orthogonal axes X and Y of coordinates, one of the axes X extending perpendicular to the feeding direction, the other axis Y extending parallel to the feeding direction. The reading head means starts to read out at a starting position in the other axis Y, the starting position in the other axis Y being preset by a counted value of scanning lines which start to be counted at the leading edge of the printing plate or printed product.
The reading head means may be located adjacent to a feed roller by which the printing plate is delivered from a plate making or direct plate making apparatus.
The reading head means may be located adjacent to a guide roller in a printing press.
The reading head means may be located adjacent to a passage through which the page of printed product is fed or dropped down in a saddle stitching book binder.